1. Field of the Invention
This invention relates generally to improvements in apparatus for producing hot mix asphalt and, more particularly, but not by way of limitation, to an apparatus for producing hot mix asphalt utilizing new aggregate and a previously manufactured and layed asphalt mix which has been reduced to form recyclable aggregate.
2. Description of the Prior Art
As can be seen from U.S. Pat. No. 470,159, issued to Warren, and U.S. Pat. No. 616,014, issued to Robbins, it has been proposed for over eighty years to recycle old asphalt paving materials for reuse in the production of new road surfaces. As early as 1912, it was recognized in U.S. Pat. No. 1,041,226, issued to Ames, that apparatus capable of recycling old asphalt mixes are particularly advantageous if they are easily transportable between working locations. However, it was not until the development of the modern turbulent mass mixing plant of the type shown in U.S. Pat. No. 2,421,345, issued to McConnaughay, that a satisfactory portable mixing plant was devised. Unfortunately, the utilization of recyclable aggregate in mixing plants constructed to apply the McConnaughay principle, as in U.S. Pat. No. 2,487,887, issued to McEachran, proved to be generally unsatisfactory due to the tendency of such apparatus to produce huge quantities of noxious blue smoke as a result of subjecting the recyclable aggregate to excessive temperatures. Primarily as a result of this disadvantage, additional generally unsatisfactory methods have been proposed for limiting the temperature of the recyclable aggregate, such as the complicated structure shown in U.S. Pat. No. 3,845,941, issued to Mendenhall.